PURIFICATION OF CARBOXYLIC ACIDS

摘要

A process for the removal and recovery of halogen components and the drying of aqueous monocarboxylic acids, particularly those produced by the reaction of an alcohol or olefin and carbon monoxide in the presence of a catalytic system comprising a Group VIII metal component and a halogen component containing bromine or iodine and at least a portion of the halogen component being either an alkyl halide or a hydrogen halide. The process comprises introducing a monocarboxylic acid stream containing water and the halogen contaminant into a first distillation column, removing an overhead fraction containing primarily alkyl halide, removing a bottoms fraction from said first distillation column containing the hydrogen halides present in said column, taking a stream from the middle portion of said first distillation column and introducing it into the upper half of a second distillation column, removing an overhead fraction consisting primarily of the water charged thereto, taking a stream from the middle portion of the second distillation column and recycling such stream to the lower half of the first distillation column, said stream containing essentially all of the hydrogen halide present in said second distillation column, and removing a product acid stream at or near the bottom of said second distillation column, the product acid stream being essentially dry and substantially free of the halogen components charged to the first column. The method is particularly applicable to the removal of water and iodine-containing compounds from acetic and propionic acids.